Being a nerd doesn't mean being pedantic. Though granted, on slashdot you may find pedantic nerds as well. ;-)
Let's face it here: you actually *knew* he was talking about 'heavier than air flight', right? As anyone with a bit of reading comprehension would understand. As any nerd with even a slither of knowledge would understand, because any nerd worth his salt knows fully well the Montgolfier brothers didn't fly for the first time in a balloon in 1916 (in the middle of WWI, thus). And since you seem pretty intelligent - seen your second paragraph - I'm sure you understood that as well. Those who didn't, aren't nerds, they're dumbasses, which you find plentiful on slashdot too these days, granted. But catering to the dumbasses makes little sense, so my guess is you were being a bit pedantic about it.
"I see a huge difference between the state of the art in aviation in 1916 vs 1903."
As do I. As does the parent poster, since that was part of his argument.
"Yes you actually can say something is impossible we have limits based on the physical universe."
Which is why I said: "It's a whole other story for things that go against the basic laws of physics, though, (such as the FTL, or 'devices' like the EM-drive, which is pure bullocks)." The parent poster didn't argument with things going against basic laws of physics, though. Let's, thus, give him the benefit of the doubt he was talking about technical difficulties.
I'll grant you that enough idiots are on slashdot that think the two are similar, and come up with things like 'the EM drive' (in fact, didn't I see such a post already?), and it's also true those same idiots quote things that people once (presumably) said were impossible, while talking about technical obstacles, instead of inherent (physical law) obstacles. And many make the faulty jump to say: "well, since that person said *that* (technological) was impossible, but he was shown wrong, it follows that *this* (physical law) which is said to be impossible, will turn out to be possible too!" (As, for instance, the first, original poster of this thread (anonymous coward), was implying, me thinks).
Those are idiots failing to see the difference, though. But I wouldn't call them nerds, since those lack even a passing knowledge of the subject at hand, nor, in fact, normal reasoning capacity.
"Tech reaches a level of maturity and then it slows."
This is largely true. But after some time of stagnation, new tech comes up which is better than the old, and replaces it. With the caveat that 'better' can also mean 'more economically' in our times, not merely technically better (though it often is, since at least on some fronts it must be superior for it to be also economically better).
If you're argumenting that normal chemical rockets are not going to reach any star soon, and certainly not in our lifetime; hey, I'm with you on that. But other things are feasible, even with current or near-term tech. You *did* look at the link I provided, I hope? The (unmanned) 'StarChip' they're proposing is technological feasible, and *could* get to the nearest star, arguably within our lifetime.
As said, I do agree with your last paragraph, that it's pretty damn unlikely we'll ever see a manned interstellar rocket land there, though. Well, unless longevity-research knows some major breakthroughs, mayhaps. ;-)